Disposable pull-on diapers having not only elasticized waist and leg opening edge portions but an elasticized below-waist portion (a portion below the waist opening edge portion) are known.
An elasticized below-waist portion of a disposable diaper is usually obtained by securing an elastic member in thread or tape form in its stretched state between two substantially inextensible sheets with an adhesive and allowing the elastic member to retract to gather the sheets. For example, Patent Document 1 discloses a method of producing a pull-on diaper including the steps of securing an elastic member for elasticizing a below-waist portion in its stretched state between two moving webs to make an outer cover elasticized in the machine direction in continuous form, spacedly fixing absorbent bodies to the outer cover of continuous form, and cutting the web assembly into individual diapers.
A stretch sheet that can be obtained without gathering a sheet material is known for use as a clothing material. In the cases where disposable diapers are produced using in a transverse feed system (a system in which a continuous web assembly having diapers continuous in the diaper transverse direction is cut into individual diapers) using such a stretch sheet, especially a highly extensible continuous stretch sheet, with its stretchable direction coincide with the machine direction, the stretch sheet is extended by the tension applied thereto while moving, and the extension percentage varies with variation of the tension. This being the case, it is difficult to stably produce disposable pull-on diapers with good finish accuracy because of positioning error or misalignment in, for example, bonding an absorbent body to the stretch sheet, making a leg hole through the stretch sheet, folding the stretch sheet in two, and joining the folded panels of the stretch sheet along predetermined seal lines.
It is conceivable to feed the stretch sheet without substantially causing the sheet to stretch in the longitudinal direction as proposed in Patent Document 2, but this requires impractically large equipment.    Patent Document 1: JP 6-296638    Patent Document 2: WO03/070140A1